Many crude oils are viscous when produced and are thus difficult, if not impossible, to transport by normal methods from their production location to a refinery.
Several methods have been suggested for the transportation of such crudes by pipeline. These include heating the crude and insulating the pipeline, adding a non-recoverable solvent, adding a recoverable solvent, and adding a lighter crude oil. These methods are, however, expensive in terms of added components and capital expenditure. It has also been suggested to form an annulus of water around the crude, but this method is technically difficult to achieve.
It has been suggested to emulsify the crude in water. To date, this method has not been found to be entirely satisfactory due to the fact that suitable emulsifiers have not been suggested.
U.K. Patent Application GB 2169220 A discloses an emulsion of crude oil in water prepared by adding an organic acid containing 8 or more carbon atoms per molecule to the crude oil, adding an aqueous alkaline solution and emulsifying the resulting mixture. This reference indicates that the viscosity of the emulsion is less than that of the crude, and the emulsion can be transported through a pipeline. Aliphatic carboxylic acids with a C.sub.8 to C.sub.30 alkyl group, e.g., stearic acid, and petroleum sulphonates are disclosed as being useful.
EPO Application 0156486 A2 discloses a method for the preparation of an HIPR (high internal phase ratio) emulsion of oil in water. The method comprises directly mixing 70 to 98% by volume of a viscous oil with 30 to 2% by volume of an aqueous solution of an emulsifying surfactant or an alkali. Mixing is effected under low shear conditions in the range of 10 to 1000 reciprocal seconds in such manner that an emulsion is formed comprising highly distorted oil droplets having mean droplet diameters in the range of 2 to 40 microns separated by thin interfacial films.
EPO Application 0184434 A2 discloses a method for reducing the salt content of a heavy crude oil. The method comprises the steps of (a) mixing 70 to 98% by volume of a heavy crude oil with 30 to 2% by volume of an aqueous solution of an emulsifying surfactant or an alkali, mixing being effected under low shear conditions in the range of 10 to 1000 reciprocal seconds in such manner that an HIPR emulsion is formed comprising distorted oil droplets having mean droplet diameters in the range of 2 to 50 microns separated by aqueous films, (b) breaking the resulting emulsion, and (c) separating the resulting mixture into a layer of relatively salt-free oil and a layer of relatively salt-enhanced water.
U.S. Pat. No. 4,776,977 and EPO Application 0214843 A2 disclose a continuous method for the preparation of an emulsion of oil in water. The method comprises initially preparing an HIPR emulsion of oil in water by directly mixing 70 to 98% by volume of a viscous oil with 30 to 2% by volume of an aqueous solution of an emulsifying surfactant or an alkali, mixing being effected under low shear conditions in the range of 10 to 1000 reciprocal seconds in such manner that an emulsion is formed comprising distorted oil droplets having mean droplet diameters in the range of 2 to 50 microns separated by aqueous films. The conductivity of the HIPR emulsion is measured, the quantity of aqueous liquid to be added as a diluent is determined, and the HIPR emulsion is diluted with the required quantity of diluent.